應用低溫成長介電膜之非晶態氧化銦鎵鋅薄膜電晶體研究

近年來，隨著消費電子產品朝向輕薄、可穿戴的發展趨勢，具有輕薄、可撓曲、耐衝擊等好處的軟性電子與軟性顯示器已成為目前顯示器發展的重要方向，也被視為下一波顯示技術革命。在軟性顯示技術中，塑膠基板是具有最佳可撓曲性且成本低廉的基板首選。然而，由於塑膠基板無法承受高溫，因此所有應用於軟性顯示技術的電子元件如薄膜電晶體、發光二極體等等，都必須發展出低溫製程，以兼容於製程需求。在低溫製程薄膜電晶體的發展上，透明氧化物半導體備受關注。氧化物半導體在非晶態下依然能保持足夠高的載子遷移率，使其可以於室溫環境下進行製程。此外，其在可見光波段具有高穿透率，可應用於透明電子或提升顯示器的開口率。另外，可低溫製程的介電材質亦是實現低溫製程薄膜電晶體的重要關鍵。將有機矽分子HMDSO和氧作為前驅物，通入ICP-CVD系統中以低溫環境成長出的矽基有機-無機複合薄膜具有優良的電性，其漏電流及崩潰電場可媲美PECVD所成長出的SiOx薄膜。且HMDSO薄膜亦在可見光波段具有高穿透率。在本研究中，我們嘗試以HMDSO有機-無機複合薄膜取代傳統常用的SiOx薄膜，來製作不同結構的非晶態氧化銦鎵鋅薄膜電晶體，並探討其電晶體特性。首先，將HMDSO有機-無機複合薄膜用於單閘極結構及雙閘極結構薄膜電晶體的下閘極絕緣層。我們發現HMDSO閘極絕緣層的元件有很小的漏電流以及很少的缺陷，並且發現雙閘極結構可以提升電晶體的載子遷移率，並降低其次臨界斜率。接著，我們將HMDSO有機-無機複合介電膜應用於下閘極薄膜電晶體的閘極介電層、蝕刻停止層及鈍化層，並且製作雙主動層結構的下閘極薄膜電晶體，得到次臨界斜率小於0.4 V/decade，且電流開關比大於10^8，具有優良開關特性的電晶體。

關鍵字

氧化物薄膜電晶體；非晶態氧化銦鎵鋅； HMDSO有機-無機複合薄膜；雙閘極薄膜電晶體；低溫製程

並列摘要

As the consumer electronics tend to become thinner, lighter and wearable in recent years, flexible displays are becoming an important trend. For flexible displays, plastics is the best substrate due to its great flexibility and low cost. However, plastic substrates cannot stand high temperatures, so all the devices on such substrates, such as thin film transistors(TFTs) and light emitting diodes(LEDs), have to be fabricated by low-temperature processes. In the development of low-temperature-processed TFTs, transparent oxide semiconductors draw wide attention. Because of their adequate carrier mobility in the amorphous state, they are compatible with low temperature processes. In addition, the high transparency permits it to be applied in transparent displays or raise the display aperture ratio. On the other hand, low-temperature-deposited dielectric films are also key to realize low-temperature fabrication. Using HMDSO and oxygen as precursors, silicon-base organic-inorganic hybrid films deposited by ICP-CVD provides good electrical properties. The leakage current and breakdown field are comparable with SiOx films grown by PECVD, and they also shows high transparency. In this study, HMDSO films are used to replace commonly used SiOx films to fabricate a-IGZO TFTs. First, we applied the HMDSO films as the bottom gate insulator of single-gate and double-gate TFTs. They show low gate leakage current and the double-gate TFTs exhibit higher carrier mobilityand lower subthreshold swing. Then, we applied the HMDSO films as the bottom gate insulator, the etch-stop layer and the passivation layer in the double-active-layer TFTs. We realized a TFT with a subthreshold swing less than 0.4 V/decade and an on/off ratio more than 10^8.